The field of the invention is the manufacture of plastic moldings utilizing injection-molding techniques to melt the plastic material utilizing ultrasonic energy.
In traditional injection molding techniques, there is a requirement that a consistent cycle is utilized to manufacture parts. This is partially due to the thermal sensitivities of the plastic polymers being processed. Under extended period of increased temperature, the plastic will degrade. To overcome the continued exposure of the plastic to high temperature, improvements in handling the plastic pellet is needed.
U.S. Pat. No. 4,469,649 pertains to an apparatus for transforming the physical characteristics of a material by controlling the influence of rheological parameters.
U.S. Pat. No. 4,793,954 describes utilization of ultrasonic vibration when applied to the thermoplastic processing apparatus such as an extruder for an injection-molding device. The ultrasonic vibration is applied to the die of the processing apparatus in a direction longitudinal to the flow of the thermoplastic.
U.S. Pat. No. 5,433,112 describes an apparatus for ultrasonically characterizing a polymer melt flowing in a predetermined direction between two opposed parallel surfaces spaced from one another to define a gap filled with polymer. Ultrasonic vibration is discussed in U.S. Pat. No. 5,885,495. See also U.S. Pat. No. 4,487,728 as to high frequency vibration and U.S. Pat. No. 3,717,427 as to a resin vibration system.
It is an objective of the patent application to utilize ultrasonic energy to rapidly heat and melt plastic pellet material and then to use a plunger to force the molten plastic into a mold cavity whereupon the ultrasonic energy is turned off allowing the polymer to re-solidify.
Described is a method of injection molding a plastic part comprising:
providing plastic pellets;
passing the pellets into a defined space in an ultrasonic horn apparatus;
applying ultrasonic energy to the horn to melt and permit flow of the plastic;
applying a force to a plunger which forces the melted plastic into a mold of a desired shape; and
recovering the desired part from the mold.